CONDENSED HOLDING COMPANY ONLY FINANCIAL STATEMENTS (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS:
Cash and due from banks		$ 64,154				$ 78,187				$ 64,154	$ 78,187
Investment securities available-for-sale		3,756				3,806				3,756	3,806
Trading securities		10,201				8,559				10,201	8,559
MBS available-for-sale		431				26,409				431	26,409
Other assets		47,359				52,040				47,359	52,040
Total assets		5,032,872				4,497,107				5,032,872	4,497,107
LIABILITIES AND STOCKHOLDERS' EQUITY:
Trust Preferred securities payable		70,680				70,680				70,680	70,680
Other liabilities		40,080				41,264				40,080	41,264
Stockholders' equity		493,947				459,725				493,947	459,725	$ 435,506
Total liabilities and stockholders' equity		5,032,872				4,497,107				5,032,872	4,497,107
CONDENSED STATEMENTS OF OPERATIONS [Abstract]
Net interest loss		33,586	$ 31,814	$ 33,070	$ 30,094	31,728	$ 31,959	$ 30,594	$ 30,255	128,564	124,536	128,487
Non-interest income		1,739	1,899	1,677	3,301	2,596	1,817	1,565	3,060	8,616	9,038	7,463
Non-interest expense		16,139	16,124	16,366	13,864	15,231	14,724	15,298	15,823	62,493	61,076	62,692
Income tax credit		8,241	7,092	7,987	7,925	7,628	7,788	7,531	7,177	31,245	30,124	29,341
Net income		11,384	10,081	11,529	11,778	11,987	11,765	10,460	10,034	44,772	44,246	43,548
CONDENSED STATEMENTS OF CASH FLOWS [Abstract]
Net income		11,384	$ 10,081	$ 11,529	11,778	11,987	$ 11,765	$ 10,460	10,034	44,772	44,246	43,548
Adjustments to reconcile net income to net cash provided by operating activities:
Net amortization										2,738	2,641	2,834
Decrease (Increase) in other assets										1,692	2,873	(8,168)
(Decrease) Increase in other liabilities										(430)	5,573	5,637
Net cash provided by operating activities										50,153	47,263	61,151
Cash flows from Investing Activities:
Proceeds from sale of investment securities available-for-sale										2,070	3,780	366
Proceeds from the sales of trading securities										1,340	7,115	131
Purchases of investment securities available-for-sale										2,134	3,884	458
Net purchases of trading securities										3,090	8,839	1,814
Principal collected on MBS available-for-sale										1,602	5,863	17,372
Net cash provided by investing activities										(553,674)	(433,935)	(168,403)
Cash flows from Financing Activities:
Treasury shares repurchased (20,000 shares during the year ended December 31, 2015)										(300)	0	0
Release of stock for benefit plan awards										251	201	293
Net cash used in financing activities										489,238	419,332	73,953
Net increase (decrease) in cash and due from banks										(14,283)	32,660	(33,299)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					78,437				45,777	78,437	45,777	79,076
CASH AND CASH EQUIVALENTS, END OF PERIOD		64,154				78,437				64,154	78,437	45,777
Holding Company [Member]
ASSETS:
Cash and due from banks		57,014				58,112				57,014	58,112
Investment securities available-for-sale		3,756				3,736				3,756	3,736
Trading securities		10,201				8,559				10,201	8,559
MBS available-for-sale		431				496				431	496
ESOP loan to subsidiary		3,028				3,222				3,028	3,222
Investment in subsidiaries		487,331				454,095				487,331	454,095
Other assets		3,867				3,798				3,867	3,798
Total assets		565,628				532,018				565,628	532,018
LIABILITIES AND STOCKHOLDERS' EQUITY:
Trust Preferred securities payable		70,680				70,680				70,680	70,680
Other liabilities		1,001				1,613				1,001	1,613
Stockholders' equity		493,947				459,725				493,947	459,725
Total liabilities and stockholders' equity		565,628				532,018				565,628	532,018
CONDENSED STATEMENTS OF OPERATIONS [Abstract]
Net interest loss	[1]									(4,779)	(4,748)	(4,851)
Dividends received from Bank	[1]									16,000	18,050	54,500
Non-interest income	[1]									295	1,376	812
Non-interest expense	[1]									(667)	(643)	(636)
Income before income taxes and equity in undistributed earnings of direct subsidiaries	[1]									10,849	14,035	49,825
Income tax credit	[1]									2,321	1,803	2,183
Income before equity in undistributed earnings of direct subsidiaries	[1]									13,170	15,838	52,008
Equity in (overdistributed) undistributed earnings of subsidiaries	[1]									31,602	28,408	(8,460)
Net income	[1]									44,772	44,246	43,548
CONDENSED STATEMENTS OF CASH FLOWS [Abstract]
Net income	[1]									44,772	44,246	43,548
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in (undistributed) overdistributed earnings of direct subsidiaries										(31,602)	(28,408)	8,460
Net gain on the sale of investment securities available for sale										4	(997)	(110)
Net (gain) loss on trading securities										108	45	(265)
Decrease (Increase) in other assets										(69)	(489)	355
(Decrease) Increase in other liabilities										(560)	1,680	(595)
Net cash provided by operating activities										12,653	16,077	51,393
Cash flows from Investing Activities:
Proceeds from sale of investment securities available-for-sale										2,000	3,780	366
Proceeds from the sales of trading securities										1,340	7,056	131
Purchases of investment securities available-for-sale										(2,134)	(3,884)	(458)
Reimbursement from subsidiary for purchases of investment securities available-for-sale										1,655	1,620	642
Net purchases of trading securities										(3,090)	(8,839)	(202)
Principal collected on MBS available-for-sale										63	72	138
Principal repayments on ESOP loan										194	179	166
Net cash provided by investing activities										28	(16)	783
Cash flows from Financing Activities:
Common stock issued for exercise of stock options										6,549	278	11,228
Treasury shares repurchased (20,000 shares during the year ended December 31, 2015)										(300)	0	0
Release of stock for benefit plan awards										251	202	293
Cash dividends paid to stockholders										(20,279)	(20,094)	(19,716)
Net cash used in financing activities										(13,779)	(19,614)	(8,195)
Net increase (decrease) in cash and due from banks										(1,098)	(3,553)	43,981
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					$ 58,112				$ 61,665	58,112	61,665	17,684
CASH AND CASH EQUIVALENTS, END OF PERIOD		$ 57,014				$ 58,112				$ 57,014	$ 58,112	$ 61,665

[1] Other comprehensive income for the Holding Company approximated other comprehensive income for the consolidated Company during the years ended December 31, 2014, 2013 and 2012.